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Back in 2019, researchers observed a collision between two black holes of wildly different masses. New analysis has revealed that the collision produced a massive recoil, sending the newly formed black hole moving so fast that it is no longer bound by the gravity of the globular cluster where it was born.

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The event was named GW190412, and it involved a black hole eight times the mass of our Sun smacking into another black hole 30 times the mass of the Sun, 3.6 times heavier than the first. The collision took place 2.4 billion light-years away, and it sent the resulting black hole flying at about 50 kilometers (31 miles) per second.

What’s special about this event is the fact that the masses were so wildly different that researchers were able to measure the “high-order modes” of the collision, which allowed the team to measure the recoil, the orbital angular momentum, and the separation of the two black holes in the couple of seconds before the merger.

“Black-hole mergers can be understood as a superposition of different signals, just like the music of an orchestra consistent with the combination of music played by many different instruments. However, this orchestra is special: audiences located in different positions around it will record different combinations of instruments, which allows them to understand where exactly they are around it,” lead author Professor Juan Calderon-Bustillo, from the Instituto Galegode Físicade Altas Enerxías, said in a statement.

The music analogy is especially apt because the asymmetry of the system actually produced two measurable harmonics that have frequencies that are a 1.5 factor apart: that’s a perfect fifth! Translated to frequencies we could play and hear, if the main frequency of the waves was a C on a piano, the overtone would be the next higher G – a perfect fifth, and incidentally, the jump in the opening two notes of Elvis Presley singing Can’t Help Falling In Love.

The chirp of the event has been recreated with computers in frequencies we can hear, although it’s not as good as Elvis. In a less rock-and-roll way, researchers had developed a new method to work out the properties ahead of this discovery. Once they finally got observations with those high-order modes, they were able to finally deploy it and learn about this event in much more detail.

“This is one of the few phenomena in astrophysics where we’re not just detecting something—we’re reconstructing the full 3D motion of an object that’s billions of light-years away, using only ripples in spacetime. It’s a remarkable demonstration of what gravitational waves can do,” co-author Dr Koustav Chandra, a postdoctoral researcher at Penn State, added.

In the 10 years since the first detection of gravitational waves, the way we study and understand them has wildly changed – and many more changes are coming.

The study is published in the journal Nature Astronomy.

A new electron diffraction method determines the room-temperature structures of solvated organic molecular microcrystals, according to a team of US-based researchers. The approach, which is presented in a preprint report and has not yet been peer reviewed, could make it easier for researchers to study molecules that need to remain solvated at all times, opening new opportunities in chemical and pharmaceutical research.

‘Many organic molecules bind water or depend on water for their structural stability, so placing such crystals in vacuum or even drying in air may alter their structure, giving erroneous results,’ explains Michael Elbaum at the Weizmann Institute of Science in Israel, who wasn’t involved in the study. He says that showing that electron diffraction can be measured on crystals embedded in liquid water is important. ‘I think that many will be surprised by this success,’ he says. ‘Room-temperature measurements in liquid water are often dismissed as hopeless, but the authors make a convincing case that their protocol solves the major issues.’ 

Microcrystal electron diffraction, or MicroED, is a powerful technique that uses high-energy electron beams (120–300eV) to illuminate tiny crystals. By analysing how these beams scattered, researchers can decode the samples’ molecular structures. ‘The interrogated crystals must resist the vacuum environment of the electron microscope and withstand the radiation from the electron beam,’ says Jose Rodriguez from the University of California, Los Angeles, in the US who led the project. He explains that freezing the samples – a strategy borrowed from cryo-EM – can help to mitigate these two effects, but only if the liquid surrounding the crystals can be frozen into glassy ice, which isn’t possible for all solvents.

‘We now show that this can also be achieved at room temperature on solvated crystals if we apply two innovations,’ says Rodriguez. The first of these strategies uses simple liquid cells to protect the crystal samples from vacuum damage. The second involves estimating a maximum tolerable exposure for each sample – to reduce damage by electron irradiation – and using new detectors and data acquisition techniques to extract as much signal as possible within that limit. ‘The detector timing to minimise beam damage was a bit of a challenge,’ Rodriguez admits. ‘It required automated software controls that have only recently become accessible.’

Rodriguez’s team tested several ways to keep crystals hydrated during their experiments and found that the best approach was to sandwich a thin liquid layer containing the crystalline samples between two thin sheets of carbon. Building the new liquid cells in this way is quite simple and only takes about 10 minutes, explains Rodriguez. ‘We use commercial transmission electron microscopy grids as the two layers of the sandwich, so that anyone can buy what they need to make them.’

To obtain the cells, the researchers activated the two carbon grids using plasma and then placed a fraction of a microlitre of the crystal slurry between them, pressing them slightly together. The team tested the method on different organic molecules including solvated pharmaceuticals like the antibiotic ceftazidime and polypeptides.

‘This is not the most engineered or perfect approach, but it is very easy to implement and requires little specialised equipment for sample preparation. We hope it can be readily implemented by many labs around the world,’ notes Rodriguez. He says that existing methods that use sandwiches made from graphene layers are less convenient because they can produce signals that interfere with the crystallography measurements. ‘We opted to use amorphous carbon instead, which is easier to access, robust, and produces little diffraction background.’